"It's a long time that" - correct or not?

I recently used the following phrasing in an fictional informal dialogue:

It's a long time that I did this.

Someone (a native speaker of English) corrected me and told me that I should use

It's been a long time since...

I then checked on Google only to find that there are 35 million hits for the phrase "It's a long time that". When I asked the person correcting me what to make of that she said that it's likely only non native speakers making the same mistake as I and she reassured me that the phrasing is not a regionalism but just plain wrong.
But I'm not sold. 35 million hits seems too much to be just made up from mistakes, plus some of the examples appear to be coming from native speakers.

• Is the phrasing grammatically correct?
• Is it a colloquial phrasing of a certain strand of English?

Well, first of all it's high time you realized you have to move on to Google Books (which shows books published and edited in English, thus providing a much more educated medium) from vanilla Google (which shows many non-native or uneducated examples).

Now, at Google Books:

"It's a long time that"

About 90 results

"It's a long time since"

About 279,000 results

ANY teacher and specialist would tell you based on the very low ratio here that the first is non-idiomatic and they would be right.

Now, this doesn't mean educated natives have never used this construct, see:

Letters of Lady Rachel Russell: from the manuscript in the ... - Page 74 Lady Rachel Russell, ‎Thomas Sellwood - 1809 IN my opinion it's a long time that I have interrupted that commerce with which you have been pleased to honour me on your part, by my omitting to make the due acknowledgments I ought for the packet of foreign letters, and your own letter .

This is a doctor writing to Lady Russell in the 18C.

You might have seen somewhere this archaic style, and memorized it. And if so, good for you, but it doesn't make it idiomatic today.

Further, what this doctor says seems to me slightly different from the "since" construct:

*"It's a long time that I have interrupted that commerce."

seems to me to mean:

"That I have interrupted that commerce it's a long time."

or, further, very roughly:

"The fact that I have interrupted that commerce is equal to a long time."

which seems to me different from the process involved in "since" where we're looking along the time axis from a point on forward.

But this is just my speculation.

BTW, before researching this, I might have accepted your sentence, but I might have told you it's dialect or similar:-)

I looked at several of the hits that came up on your Google search and most of them appear to be non-native, appear to mean something else, or are broken up by other punctuation.

Native speakers have weighed in that it doesn't sound natural and, as another native speaker, I'm weighing in as well: It doesn't sound natural.

I don't disagree with the other answers, particularly the point that your construction sounds stilted. But the vital point that seems to have been missed is that that and since would have opposite meanings there. "It's a long time that I have been writing English" is, though peculiar, both grammatical and correct: I have been writing English since childhood, which is a long time now. "It's a long time since I wrote English" is also grammatical, though incorrect, (or possibly, since the sentence is itself English, paradoxical). *"It's a long time that I wrote English" is ungrammatical (misuse of tenses) and the reader is left in doubt about which of the two was intended.